1. Field of the Invention
This invention is concerned with a gear type transmission which disposes an input shaft coaxially to an output shaft, and is used in automobiles or other vehicles.
2. Description the Related Art
A conventional gear type transmission which disposes the input shaft coaxially to the output shaft is shown in the repair manual of the TOYOTA R50 TRANSMISSION. In such a conventional transmission, as shown in FIG. 2, an input shaft 22 and an output shaft 23 are coaxially disposed in and supported with a casing 21, so that each of the shafts 22,23 is freely rotatable. A counter shaft 24 is supported by the casing 21 parallel to the shafts 22, 23, and freely rotatable with respect thereto. An input gear Ing is fixed on one end of the input shaft 22 and engages with a counter input gear CIng fixed to the counter shaft 24. A third gear 3g'is rotatably mounted on the output shaft 23 and engages with a counter third gear C3'g fixed to the counter shaft 24. A second gear 2g'is rotatably mounted on the output shaft 23 and engages with a counter second gear C2g'fixed TO the counter shaft 24. A first gear 1g'is rotatably mounted on the output shaft 23 and engages with a counter first gear C1g'fixed to the counter shaft 24. A fifth gear 5g'is fixed to the output shaft 23 and engages with a counter fifth gear C5g' rotatably mounted on the counter shaft 24. A third-fourth synchronized equipment 25 is set between the input shaft 22 and the output shaft 23. By the shifting of a sleeve of the synchronized equipment 25, the third gear 3g'may be connected indirectly to the output shaft 23 in a third gear position to rotate simultaneously with the output shaft 23. The input shaft 22 connects in a fourth gear position directly. A first-second synchronized equipment 26 is between the first gear 1g'and the second gear 2g'on the output shaft 23. By the shifting of a sleeve of the synchronized equipment 26, the first gear 1g' may connected in a first gear position indirectly to the output shaft 23 to rotate simultaneously with the output 23. In a second gear position, the second gear 2g' connects directly to the output shaft 23 to rotate simultaneously with the output shaft 23. A reverse gear Rg' is formed on the outer periphery of the sleeve of the first-second synchronized equipment 26, and by the shifting of the sleeve, to a reverse shift position, the transmitting force of the counter reverse gear CR'g is transmitted to the output shaft 23 through an idle gear (not shown in FIG. 2) disposed between the reverse gear R'g and the counter reverse gear CR'g. A fifth synchronized equipment 27 is mounted on the counter shaft 24, and by the shifting of the sleeve, to a fifth gear position, the counter fifth gear C5'g connects to the counter shaft 24 to rotate simultaneously with the counter shaft 24.
In the conventional transmission the first-second synchronized equipment 26 is fixed to the output shaft 23 and the counter shaft 24 rotates as a result of the transmission of tongue from the input shaft 22. Therefore, when the transmission is shifted to the first shift position, the operating force for the shifting of the first and second synchronized equipment 26 includes not only the force required to synchronize the output shaft 23 to the moment of inertia of the first gear 1g', but also the force necessary to synchronize the output shaft 23 to the moments of inertia of the counter shaft 23, and the input shaft 22. Therefore a large force is needed to shift gears. In particular, the synchronized equipment at lower gears requires a large shifting force.
The loading tongue operating on the pair of the shift gears is expressed by Tex, wherein Te.times..lambda.i is the input tongue from the input shaft 22, and .lambda.i is the reduction ratio between the input gear Ing and the counter input gear CIng. Each of the pairs of the shift gears must be designed for lasting quality in view of the tongue value. Therefore, the gear teeth must be increased in width and the increases corresponding in size and weight. The bearings transmission must also be designed to withstand heavier loads.
Further, the relative rotational parts between the first, second and third gears 1g', 2g', 3g' and the output shaft 23 are positioned in the upperpart of the casing 21. Therefore, lubricating oil may not be supplied to these relative rotational parts sufficiently. Particularly at higher speeds, the gears 1g', 2g', 3g' rotate continuously relative to the output shaft 23. Accordingly, the gears and the output shaft may be damaged.